Spelling suggestions: "subject:"heavy ion collision."" "subject:"leavy ion collision.""
41 
A search for the H0 dibaryonJensen, Paul Thomas 21 March 2011 (has links)
Not available / text

42 
A model for proton, deuteron and pion production in relativistic heavy ion collisions /Gale, C. (Charles) January 1982 (has links)
No description available.

43 
Angular distributions from heavyioninduced fissionViola, V. E. January 1961 (has links)
ThesisUniversity of California, Berkeley, 1961. / "UC4 Physics" t.p. "TID4500 (16th Ed.)" t.p. Includes bibliographical references (p. 8891).

44 
Studium tvrdých procesů ve srážkách těžkých iontů na detektoru ATLAS / Study of hard processes in heavy ion collisions at ATLASŠtefko, Pavol January 2015 (has links)
Jet production in PbPb collisions at a pernucleon centerofmass energy of 2.76 TeV has been studied using the ATLAS detector at the LHC. Interactions between the high pT partons and the hot, dense medium, produced in these ultrarelativistic collisions, are expected to cause the loss of the jet energy (jet quenching). This thesis presents results of the jet analysis done on the data taken during the 2011 heavyion run at the LHC as well as PYTHIA Monte Carlo reference. Jets are reconstructed using the antikt jet clustering algorithm and studied as a function of collision centrality and dijet energy imbalance. With increasing centrality, dijets are observed to be increasingly asymmetric, consistent with the theory of jet quenching. The study of charged particle tracks indicates the increase of the lowpT tracks in the strongly quenched jets. 1

45 
A model for proton, deuteron and pion production in relativistic heavy ion collisions /Gale, C. (Charles) January 1982 (has links)
No description available.

46 
Collectivity in Large and Small Collision Systems: Flow in Xe+Xe Collisions and Sensitivity to the Presence of Hard Scatterings in pp CollisionsYin, Pengqi January 2023 (has links)
The QuarkGluon Plasma (QGP) produced in heavyion collisions has been shown to behave like a nearly perfect fluid, characterized by a very low ratio of shear viscosity to entropy density. Significant measurements in large collision systems have improved the constraints on the value of 𝜂/𝑠. However, the precise temperature dependence of 𝜂/𝑠 still remains unknown. The interplay between viscous effects and initial geometry fluctuations is important that requires further investigation. Another key open question in the study of multiparticle production is the relationship between the “ridge” – observed azimuthal correlations between particles in the underlying event that extend over all rapidities – and hard or semihard scattering processes in small collision systems. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event.
This dissertation presents two analyses. The first analysis measures flow harmonics 𝜈2–𝜈6 in 3 𝜇b^1 of Xe+Xe collisions at √𝑠𝖭𝖭 = 5.44 TeV using the ATLAS detector at the LHC. The centrality, multiplicity, and 𝑝_T dependence of the 𝜈n values obtained using twoparticle correlations and templatefit procedure are presented, and the measurements are compared with those in Pb+Pb collisions and 𝑝+Pb collisions at 5.02 TeV. The 𝜈n values in Xe+Xe collisions are observed to be larger than those in Pb+Pb collisions for n = 2, 3, and 4 in the most central events. However, the 𝜈n values in Xe+Xe collisions become smaller than those in Pb+Pb collisions with decreasing centrality or increasing harmonic order n. The 𝜈n in Xe+Xe and Pb+Pb collisions are also compared as a function of the mean number of participating nucleons and the measured chargedparticle multiplicity in the detector. The 𝜈3 values in Xe+Xe and Pb+Pb collisions are observed to be similar at the same ⟨𝑁_part⟩ or multiplicity, but the other harmonics are significantly different.
The second analysis studies twoparticle correlations in pp collisions at 13 TeV using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of 15.8 pb⁻¹, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Secondorder flow coefficients, 𝜈2, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.

47 
Ion beam mixing of Mo/Al bilayer samples and thermal spike effectsChen, GengSheng January 1987 (has links)
Metallic bilayer samples of Mo(400 Å)/ Al(substrate) were characterized using Rutherford Backscattering Spectroscopy after first being irradiated with Xe ion beam having an energy of 1.8 MeV. The computer code RUMP was then used to simulate the RBS spectra. The interdiffusion at the interface was considered in terms of thermal spike induced atomic migration. It was found that the coupling of the chemical effect with spike is significant with regard to mixing of the bilayer samples. Furthermore, in addition to the initial contamination of carbon atoms on the surface and at the interface, more carbon atoms were found to be picked up by the surface, this carbon w.as from the vacuum pumps and tended to migrate into the surface once irradiation dose exceeded 11 x 10¹⁵cm².
A semiempirical model was developed for ion beam mixing taking into account collisional mixing and thermal spike effects, as well as the thermal spike shape. The collisional mixing part was accounted for by the KinchinPease model, or, alternatively dynamic Monte Carlo simulation. For the thermal spike, the ion beam mixing parameter Dt/Φ was derived to be proportional to (  F<sub>D</sub> /ΔH<sub>coh</sub>)<sup>2+μ</sup>, where F<sub>D</sub> is the damage energy deposited per unit path length, ΔH<sub>coh</sub> is the cohesive energy of the target materials, and µ is a constant dependent on the spike shape and point defect density in the spike regions. The thermal spike introduces a nonlinear effect in the mixing process, distinguishing itself from the linear effect of ballistic mixing. The shape of the thermal spike that best fit the experimental results depends on the magnitude of the cascade density. For relatively high density collisional cascades, where thermal spikes start to be important, it was found that a spherical spike model was more consistent with experimental measurements at low temperatures. However, for extremely high density collisional cascade regions, a cylindrical shaped spike gave better results.
The atomic migration energy in the spike regions is scaled by a factor of one out of 8.6 of cohesive energy. The migration mechanism was recognized to be interstitialdominated one. / M.S.

48 
Gaussian and nonGaussianbased GramCharlier and Edgeworth expansions for correlations of identical particles in HBT interferometryDe Kock, Michiel Burger 03 1900 (has links)
Thesis (MSc (Physics))University of Stellenbosch, 2009. / Hanbury BrownTwiss interferometry is a correlation technique by which the size and shape
of the emission function of identical particles created during collisions of highenergy leptons,
hadrons or nuclei can be determined. Accurate experimental datasets of threedimensional
correlation functions in momentum space now exist; these are sometimes almost Gaussian
in form, but may also show strong deviations from Gaussian shapes. We investigate the
suitability of expressing these correlation functions in terms of statistical quantities beyond
the normal Gaussian description. Beyond means and the covariance matrix, higherorder
moments and cumulants describe the form and di erence between the measured correlation
function and a Gaussian distribution. The corresponding series expansion is the Gram
Charlier series and in particular the GramCharlier Type A expansion found in the literature,
which is based on a Gaussian reference distribution. We investigate both the GramCharlier
Type A series as well as generalised forms based on nonGaussian reference distributions,
as well as the related Edgeworth expansion. For testing purposes, experimental data is
initially represented by a suite of onedimensional analytic nonGaussian distributions. We
conclude that the accuracy of these expansions can be improved dramatically through a
better choice of reference distribution, suggested by the sign and size of the kurtosis of
the experimental distribution. We further extend our investigation to simulated samples
of such test distributions and simplify the theoretical expressions for unbiased estimators
(kstatistics) for the case of symmetric distributions.

49 
Eventbyevent Hydrodynamics for LHC / Hidrodinâmica Eventoporevento para o LHCMachado, Meera Vieira 06 August 2015 (has links)
We perform an eventbyevent hydrodynamic analysis for PbPb collisions at the incident energy of sqrt(sNN) = 2.76TeV, also studying the effects of two equations of state under the same initial conditions and freezeout scenario: one characterized by a critical point and the other based on Lattice QCD (Quantum Chromodynamics) calculations. The observables of interest are particle spectra in terms of pseudorapidity and transverse momentum, as well as flow harmonics, which are coefficients that carry information on the initial anisotropies of the system throughout its evolution. Those are computed and compared with experimental Large Hadron Collider (LHC) data. There are slight differences in the results for each equation of state, caused by their distinct features. Lastly, the LHCbased calculations are compared with previous works related to the Relativistic HeavyIon Collider (RHIC) experimental data. The main techniques of the latter are performed in this work, which results in differences between some aspects in the outcome for each collision type, from initial energy distributions to freezeout temperatures. / É feita uma análise de hidrodinâmica eventoporevento para colisões de PbPb à energia incidente de sqrt(sNN) = 2.76TeV. Estudamos os efeitos de duas equações de estado sob as mesmas condições iniciais e desacoplamento: uma é caracterizada por um ponto crítico e a outra é baseada em cálculos de Lattice QCD (Cromodinâmica Quântica). Os observáveis de interesse são os espectros de partículas em termos da pseudo rapidez e momento transversal, assim como os coeficientes harmônicos de Fourier que, por sua vez, carregam as anisotropias iniciais do sistema durante toda a sua evolução. Tais observáveis são calculados e comparados com dados experimentais do Large Hadron Collider (LHC). Por fim, os cálculos baseados em parâmetros referentes às energias do LHC são comparados com trabalhos anteriores feitos com base em dados experimentais do Relativistic HeavyIon Collider (RHIC). Os principais métodos usados no caso anterior são aplicados a este trabalho, o que resulta em algumas diferenças entre os resultados dos dois tipos de colisão, desde a distribuição de energia inicial a temperaturas de freezeout.

50 
Produção de Mésons Vetoriais em Processos FotoInduzidos no LHC / Vector Meson Production in Photoinduced Processes at LHCMoreira, Bruno Duarte da Silva 26 April 2017 (has links)
O advento dos colisores modernos tem proporcionado novas possibilidades de estudo em física de partículas como, por exemplo, a busca por nova física e o estudo de novos estados da matéria hadrônica. Em particular, em colisões de íons pesados em altas energias, acreditase que um novo estado da matéria seja formado antes da colisão, o chamado condensado de vidros de cor. Tal estado seria a condição inicial de um plasma de quarks e glúons e é caracterizado por altas densidades de pártons (quarks e glúons). De fato, as equações de evolução da Cromodinâmica Quântica predizem que, para virtualidades moderadas e altas energias, os hádrons se tornam sistemas extremamente densos devido ao crescimento das distribuições de glúons nessas condições. Um crescimento indefinido das distribuições de glúons poderia levar à violação do vínculo de unitariedade. Para evitar essa violação, existe um mecanismo chamado de saturação de pártons o qual contém o crescimento das distribuições de quarks e glúons de forma a respeitar o vínculo de unitariedade. Teoricamente, no limite de altas energias, observase que os hádrons são populados especialmente por glúons. Experimentalmente, existem indícios da saturação em colisões ep, pp, pA e AA, contudo, isso ainda é uma questão em aberto. Portanto, no limite de altas densidades, espera se que a física não linear, a qual leva em conta efeitos de recombinações de glúon, passe a se manifestar. Uma alternativa para o estudo da saturação em colisores hadrônicos são os processos fotoinduzidos, os quais ocorrem em interações ultraperiféricas. Em uma colisão ultraperiférica entre dois hádrons, o parâmetro de impacto é maior do que a soma dos raios dos hádrons, de forma que interações fortes são suprimidas. Dessa forma os hádrons atuam como fontes de fótons (quase reais) podendo ocorrer interações fótonhádron e fótonfóton. Nesse trabalho estudamos a fotoprodução difrativa de mésons vetoriais em energias do LHC para colisões ultraperiféricas prótonpróton, prótonnúcleo e núcleonúcleo e a produção dupla de mésons vetoriais em colisões fótonfóton e devido ao mecanismo de duplo espalhamento fótonp(A). Mostramos como esses processos podem ser usados para estudar a física de altas energias e os efeitos de saturação. Os efeitos de saturação em nossos cálculos são levados em conta através do formalismo de dipolo de cor, que é uma das ferramentas básicas usadas nessa tese. O tratamento de colisões ultraperiféricas hádronhádron foi feito com a aproximação de fótons equivalentes que assim como o formalismo de dipolo, foi extensamente usada. Nossos resultados apontam que o estudo fenomenológico e experimental dos tipos de processos citados acima são factíveis e podem ser usados para vincular a dinâmica da QCD em altas energias. / The advent of the modern colliders has provided new possibilities of study in particle physics as, for example, the search for new physics and the study of new states of the hadronic matter. In particular, in high energy heavy ion collisions is expected that a new state can be formed before the collision, the so called Color Glass Condensate. This state would be the initial condition of the Quark Gluon Plasma and is characterized by high parton (quarks and gluons) densities. Indeed, the Quantum Chromodynamics evolution equations predict that, for moderate virtualities and high energies, the hadrons become extremely dense systems due to the growth of the parton distribution in these conditions. An indefinite growth of the parton distributions could lead to the violation of the unitarity bound. To avoid this violation, there is a mechanism called parton saturation which tames the growth of the parton distributions to satisfy the unitarity bound. Theoretically, in the high energy limit, one can see that the hadrons are populated mainly by gluons. Experimentally, there are indications of the saturation in ep, pp, pA and AA collisions, however, this is an open question. So, in the high density limit, we expect that the nonlinear physics, which takes into account gluon recombination effects start to manifest itself. An alternative for the study of the saturation at hadronic colliders are the photoninduced processes, which occurs in ultraperipheral collisions. In a ultraperipheral collision between two hadrons the impact parameter is greater than the sum of the radii of the hadrons, so the strong interaction is suppressed. Thus, the hadrons act as sources of (almost real) photons and may occur photonhadron and photonphoton interactions. In this work we study the diffractive photoproduction of vector mesons at LHC and future colliders energies in ultraperipheral protonproton, protonnucleus and nucleusnucleus collisions and the double vector meson production in photonphoton collisions and due to the double photonp(A) scattering mechanism. We show how these processes can be used to study the high energy physics and the saturation effects. These effects are considered in our calculations through the color dipole formalism, which is one of the basic tools used in this thesis. The treatment of the ultraperipheral hadronhadron collisions was done through the equivalent photon approximation that just as in the dipole formalism, was widely used. Our results point that the phenomenological and experimental studies of the processes cited above are feasible and can be used to constraint the QCD dynamics in high energies.

Page generated in 0.0985 seconds